


Railed on the Rails

by ruff_ethereal



Category: BanG Dream! (Anime), BanG Dream! Girl's Band Party! (Video Game)
Genre: F/F, Futa!Kasumi, Futanari, Incest, Sibling Incest, Train Sex, Unsafe Sex
Language: English
Status: Completed
Published: 2020-06-27
Updated: 2020-06-27
Packaged: 2021-03-04 06:47:38
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 1,636
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24939289
Author URL: https://archiveofourown.org/users/ruff_ethereal/pseuds/ruff_ethereal
Summary: Asuka finds herself trapped in a stalled, crowded train car with a very horny Kasumi.
Relationships: Toyama Kasumi/Toyama Asuka
Comments: 4
Kudos: 62





	Railed on the Rails

**Author's Note:**

  * For [tinygaydream](https://archiveofourown.org/users/tinygaydream/gifts).



> I wrote this entire fic specifically for the person I gifted it to. Don't expect more.
> 
> I am also embarrassed by that title but I don't have the time to think of a better one.

If there is one good thing about the train suddenly suffering a breakdown one morning, it is that Asuka did not have a test, a quiz, or any other important school business she was going to miss.

“Asuka…!”

If there was one of many _bad_ things about the train suddenly suffering a breakdown, it was that Asuka was riding with Kasumi and was wrapping her arms around Asuka’s shoulders and pulling on her like a panicked child.

“Big Sis!” Asuka snapped. “Will you please calm down already?!”

"But the train's stopped, Acchan…!" Kasumi whined. "We don't know how long it's going to take to start moving again! What if we're stuck here all day?! Oooh, I thought I was only going to have to hold it in till we got to school...”

Asuka felt a heat rising in her cheeks, wetness growing in her panties as she feels Kasumi's bulge pressing, rubbing, throbbing against her back and her butt. _“Gah, why can’t Big Sis have_ normal _problems she needs to solve in the bathroom…?”_ she thought.

Kasumi nestled her chin on Asuka’s shoulder and looked at her with her “Poor Neighborhood Stray” face.

Asuka glared at her and said, “Stop it, it’s not like you’ll die if you don’t get relief!”

“But it feels like I already am…!” Kasumi whined. “Please help me, Acchan?”

“We’re in the _train!”_ Asuka hissed as loudly as she dared.

“Please…?” Kasumi whimpered.

“We’re completely stopped! Someone might notice us! I-I’m right against the window, damn it!” Asuka whispered, her voice getting shakier and weaker the longer she spoke.

Kasumi leaned in closer and brought their faces close together, Asuka could see her features in all their sympathy-inducing glory, especially her purple eyes glistening with tears. “Please?” Kasumi squeaked.

“ _Ugh!”_ Asuka cried. She panicked as she got the attention of some of the other bored and stranded passengers around them, began to relax as they returned to their phones or books. Much, _much_ more quietly, she said, “Fine—but you can only finish _once.”_

“Yay!” Kasumi whispered, all sparkles and smiles once more. “You’re the best, Acchan!”

Asuka huffed. “I’m only doing this so you’ll stop bothering me,” she said as she discretely spread her legs, crossed her arms and braced herself against the window.

“I’m going to put it in your pussy, okay?” Kasumi whispered as Asuka felt her hands move up her skirt.

“My--?!” Asuka began before she yelped—the train may have stopped moving but the AC was still doing just fine. “W-Why my pussy, Big Sis?!”

“Because it’ll be too awkward and obvious if I put it up your butt!” Kasumi whispered as Asuka felt her warm, calloused fingers on her wet pussy.

Asuka scowled. “Like this isn’t already awkward and ob--” she clapped her hand over her mouth to muffle a moan. “Big Sis...” she hissed as she began to tremble and leak, “ _warn me_ before you stick it in…!”

“But I didn’t stick it in,” Kasumi whispered back as Asuka felt her begin to pump her fingers in and out. “That was just my fingers—and wow, you’re really, _really_ wet right now, Acchan!”

“Dummy!” Asuka snapped. “Stop fingering me and just put it in already!”

“Okay…!” Kasumi hummed as she abruptly pulled her fingers out, Asuka had to bite back another moan. “Since you seem to want me to fill you up as much as I want to empty out...”

“I don’t want anything except for you to--” Asuka nearly bit her tongue as she made an undignified noise. She discretely looked around, saw that no one was paying attention to them, then snapped, “Dummy…! _Pull_ it out, don’t let it spring up between my legs like that! What if you fling your goo all over our clothes?! How are we going to explain _that?!”_

“Maybe we can ‘accidentally’ spray water on ourselves at a fountain and then change into our PE clothes?” Kasumi asked as she pulled her throbbing, leaking cock away from Asuka’s inner thigh.

“Every day, you make me question how we could possibly be sisters,” Asuka grumbled. She gasped as she felt Kasumi’s press her messy cockhead against her pussy.

“I’m going to put it in now, Acchan!” Kasumi hummed.

“Wait--!” Asuka squeaked.

In their reflections, Asuka saw Kasumi blink in confusion, herself as she pulled her handkerchief out, wadded up a portion, and bit down on it. She was going to soak it in drool and render it useless and gross for the rest of the day but _that_ was better than a whole train car of strangers finding out she was getting railed by her sister.

With her luck, someone would post the entire incident on the internet and that would be it for the both of them socially and professionally for Kasumi.

“Ready _now_ , Acchan?” Kasumi asked.

As discretely as she could while biting down on her handkerchief, Asuka nodded.

“One, two--!”

Asuka made a muffled, pleasured squeal as she felt Kasumi penetrate her, her cock spurting and spilling fresh goo inside her, her girth spreading her open and rubbing against her inner walls.

“Ahh...” Kasumi sighed. “Your pussy is the best, Acchan!”

“ _Shut up!”_ Asuka thought as she bit down harder on her handkerchief. _“Shut up, shut up, shut up! Go blow a load inside me already, someone could find us out at any moment…!”_

“I’m going to start moving now, okay, Acchan?” Kasumi whispered.

“ _Go! Go!_ Go!” Asuka thought as looked down and away from her reflection, so she wouldn’t see the redness in her cheeks, the look in her eyes, or the dark stain around her teeth growing bigger and bigger.

Kasumi began to thrust—messy, clumsy, without a hint of rhythm or any serious attempt to try and get into it. When they had sex, Asuka found it hard to believe that Kasumi was a musician, that she could both sing and play rhythm guitar as well as she did when she was so poor at something this mechanically simple and instinctive.

“Ah, Acchan…!” Kasumi sighed. “You’re so wet and tight, you’re making me feel so _good~!”_

But that was her appeal, wasn’t it? Kasumi lived life at the melody of her rhythm guitar, on-stage, in the bedroom, or here in a crowded and stalled train car.

Asuka couldn’t discern her thoughts, what she was planning, what she was going to do next, always kept off-balance and left guessing and forced to accept things as they came. The only thing she _was_ sure of right now was that she loved every moment of Kasumi’s cock thrusting in and out of her pussy, her gooey pre-cum spreading all over her inner walls, Kasumi’s heated whimpers and breaths as she pleasured herself.

“Ah—Acchan, I’m cumming…!”

Acchan’s jaw _ached_ from how hard she clamped down on that soaked, sticky wad of cotton and spit, she fell forward and slumped against the door, her legs no longer quite capable of keeping her up as knees trembled and shook, her arousal dripped down her inner thighs and to tiny puddles on the floor, she felt Kasumi’s hot goo fill her up.

“Phew…!”

Kasumi’s orgasm faded, Asuka felt her quickly pull out and tug Asuka’s panties back up before too much of her goo could spill out from her pussy and onto the floor. The rest ended up soaking her panties, a sticky, hot, gooey mess spreading out all over her crotch. Asuka prayed this train would start moving soon before it all cooled, dried, and turned into a _very_ unpleasant sensation.

“That’s one!” Kasumi said as she pulled her hips back then hugged Asuka around her shoulders again. “Thanks, Acchan! I’m pretty sure that I’ll last until we get to school now—unless we stay trapped here till lunch…?!”

Asuka sighed as she pulled the handkerchief from her teeth. She stretched and flexed her sore jaw for a few moments before she said, “I doubt _anyone_ will stand to let us wait that long, Big Sis.”

The train eventually started moving again, they arrived at their station and were issued certificates as was standard. Inevitably, the line at the women’s bathroom stretched on and on and unwilling to be even later than they already were, Asuka settled for hiding behind a tree and some bushes with Kasumi looking “natural” as she kept watch nearby.

Asuka sighed as she removed her ruined panties, squatted and cleaned herself down as best as she could with some wet wipes, then stepped into the fresh extra pair she kept in her bag. “You owe me a new pair of panties,” she said as all the evidence was hastily tossed into a nearby trash can. _“Again.”_

“Hehe,” Kasumi said as she rubbed the back of her head. “Don’t worry, Acchan! Big Sis is going to take responsibility for that…!”

“You had better!” Asuka yelled. Then, she stopped, looked away, and said, “Um, I also just realized that I forgot to buy new emergency birth control...”

Kasumi smiled and pulled her in for yet another hug. “Don’t worry, Acchan,” she whispered, “Big Sis will take responsibility for that, too.”

“You will…?” Asuka whispered as she looked up at Kasumi.

“Of course,” Kasumi said. Then, she pulled away and whipped out her phone. “Kokoro gave me a number to text specifically for emergencies like this!”

Asuka blinked. “I—what?”

“She and Misaki worry about it all the time so she decided to give all of us at CiRCLE help if we need it!” Kasumi said.

Asuka choked, torn between two _very_ conflicting emotions.

Soon, a black luxury vehicle arrived with black-suited, sunglasses-wearing women bringing emergency contraceptives and offering a ride to school. Kasumi and Asuka happily took it but Asuka never told her just why she spent the whole ride sulking in one corner.


End file.
